Traditionally, such devices, also called analysis machines, make it possible to automate certain protocols, such as for example pipetting liquids into gel cards. This protocol consists of pouring a predetermined quantity of liquid into a reactive well of a gel card containing one or more reagents. This liquid can for example be a blood sample, or any other type of human sample.
In a known manner, a gel card is a receptacle containing one or more reactive wells that are initially sealed by a cap. After having pierced the cap and poured the liquid, chemical reactions occur between the poured liquid and the reagent(s) of the card.
Generally, the quantity of liquid poured is very small, in the vicinity of several microliters, so that one generally refers to a “dose.” What is more, the filling of the wells must respect certain quality criteria. Among these criteria, we will more particularly mention those relative to the creation of an air gap between the dose of liquid dispensed into the well and the reagent previously present at the bottom of the well, as well as the criterion relative to the absence of liquid splashes on the inner wall of the well. Splashes most often come from more or less significant, but still random, fracturation of the dispensed dose of liquid.
The presence of an air gap has the effect of provisionally prohibiting physical contact between the dispensed dose of liquid and the reagent. One interest is of controlling the moment from which the chemical reaction must begin. In practice, the gel cards are incubated and centrifuged after dispensing the liquid dose thereby leading to the chemical reaction.
The absence of splashes in turn is necessary in order to prevent a fraction of the dose of liquid from remaining stuck to the walls of the well and thus being removed from the incubated and centrifuged reactive mixture.
To resolve the first problem, document U.S. Pat. No. 5,780,248 proposes the use of consumable accessories made from plastic, said accessory being formed by an insert provided with six cavities with a pointed lower end. Moreover, the lower ends of the cavities are provided with a very small hole. This accessory is intended to be manually planted in a gel card, the ends of the cavities perforating the cap sealing the wells of the gel card. Each of the cavities of the accessory is housed in a well of the gel card. Then, a dose of liquid is dispensed into each of the cavities of the accessory. Using that accessory, the operator does not need to worry about whether an air gap is formed, inasmuch as the cavity isolates the dispensed liquid dose from the reagent contained at the bottom of the well. It also appears that the use of such accessories makes it possible to decrease the presence of splashes.
However, this solution has several drawbacks: the accessories must be purchased, stored and handled. What is more, the installation of the accessories on the gel cards must necessarily be done manually, which is inconvenient and not very fast.